Sexual Selection

Question 0

How to distinguish between the two sexes across sexually reproducing species?

Answer 0

Gamete size - male gametes/sperm are a lot smaller than female gametes/eggs (typically)

Question 1

Sexual dimorphism

Answer 1

Phenotypic differences between males and females of the same species (peacocks, lions)

Question 2

Sexual selection

Answer 2

Differences in fitness caused by differences in mating success among individuals of the same sex, leads to evolution of traits that increase mating success, explains traits that don’t make sense I’m the context of other aspects of the environment (social environment is powerful)

Question 3

Reproductive investment

Answer 3

Males - sperm are cheap and less parental care is provided

Females - eggs are more expensive and more parental care provided

Question 4

Limits on reproductive success

Answer 4

Males - limited by number of females acquired as mates

Females - limited by resources to produce young

Question 5

Greater variation in naïf success typically

Answer 5

Males (fail to mate vs how many mates found)

Question 6

Competes for mates

Answer 6

Males typically - invest less time and effort in offspring

Question 7

Choosy sex

Answer 7

Females typically - invest more time and effort

Question 8

Stronger sexual selection

Answer 8

Males - compete with others for females (armaments) or attract females (ornaments)

Question 9

Intrasexual selection

Answer 9

Male-male competition, evolution of male traits (armaments) associated with combat, sperm competition and infanticide

Question 10

Intersexual selection

Answer 10

Female choice, evolution of male traits (ornaments) associated with good genes, simulations of female sensory biases and sexy sons/run away selection

Question 11

Male combat traits

Answer 11

Leads to evolution of traits for aggressive interactions with other males one access to females

Question 12

Sperm competition

Answer 12

Competition between males that have mated with the same female to determine whose sperm will fertilize the eggs, requires multiple mating by females and internal fertilization

Question 13

Sperm competition traits

Answer 13

1. Transfer lots of sperm or large sperm
2. Remove, displace, destroy sperm of other males
3. Produce a copulatory plug, guard female

Question 14

Infanticide

Answer 14

Kill off infants of previous males when a new male wins control of an area/group of females so that females will be ready to copulate more rapidly and produce offspring of the new males

Question 15

Male lions and infanticide

Answer 15

Removes competitors genes, females in pride ready to mate sooner

Question 16

Female choice traits

Answer 16

Direct benefits (parental care, resources), good genes, traits that are honest indicators of males having better genetic quality

Question 17

Direct benefits from female choice

Answer 17

Parental care (strength and protection), resources (food)

Question 18

Explanations why female choice may not always be correlated with direct benefits

Answer 18

Females choose males with traits that are honest indicators of their genetic quality (good genes), sensory bias, sexy sons

Question 19

Good genes

Answer 19

Males that are honest indicators of their genetic quality

Prediction: offspring of males with preferred traits are more likely I survive/thrive

Question 20

Runaway sexual selection or sexy sons

Answer 20

Females choose males that are attractive in order to produce attractive sons

Question 21

How preferences evolve and why prefer them in the first place?

Answer 21

1. Some females prefer a particular trait
2. Males with trait have slightly higher fitness thus sons inherit sexy trait and daughters inherit preference for sexy trait, more females then prefer trait and males have even higher fitness with trait (snowball effect)
   Genetic drift of preference allele, good genes and sensory bias

Question 22

Female sensory bias

Answer 22

Females choose males with traits that exploit their pre-existing sensory biases
Prediction: preferred male traits resemble other cues that females respond to in the environment

Question 23

Multiple forms of sexual selection?

Answer 23

Sexual selection mechanisms are not mutually exclusive and can work together